As most commonly practiced, sailboat masts are designed to be held upright by a system of guy wires: typically a forestay, a backstay, and usually two or more pairs of lateral shrouds attached to the hull by chain plates. If the mast is stepped deep inside the hull, it may receive sufficient support part way up by a deck or cabin-top to hold the mast upright sufficient for maintenance work, e.g. for mast removal by a shore-based travel lift or crane, but not sufficient for sailing. Alternatively, in “tabernacle” mounting, the mast is stepped on the deck or cabin top, where a hinged attachment allows the mast to be lowered en route, e.g. to clear an overhead bridge, usually by inclining the mast forward. However, the “tabernacle” hinge generally cannot be made to hold the mast upright, even temporarily, without the necessary shrouds and stays.
In contrast to the stayed mast category as described above, in a special un-stayed mast category, addressed by the present invention, the sailboat and its mast are designed to sail without requiring any support from guy wires such as stays and shrouds.
As shown in FIG. 1 in a cross-sectional representation, an un-stayed mast 10 is held upright entirely by its lower end region being fitted in a cantilever manner into a strong receptacle 12 configured in the sailboat structure 14, usually in a deck or cabin top. The weight of the mast 10 rests on a support member or floor at the bottom of the receptacle 12, which will generally require drainage to prevent water accumulation.
The cross-sectional shape of the mast 10 and receptacle 12 is a matter of design choice and could include round, oval, rectangular or square. The mast 10 and receptacle 12 need not have identical cross-sectional shape, e.g. they could be circular and square, tangent at four places, and should be dimensioned for a slide fit so the mast 10 can be readily removed by pulling it upwardly and out of the receptacle 12.
A round cross sectional mast shape has the advantage that the mast 10 can be allowed to rotate for sailing purposes: annular sleeves or bearings may be placed near the upper and lower ends of the receptacle 12, and/or a ball or other form of thrust bearing may be deployed at the bottom to carry the weight of the mast 10.
Typically this category of cantilevered un-stayed rig has been viable for single-handed manual mast stepping and un-stepping only in small sailboats up to about 20 feet. With the sailboat underway in the water, or even docked, mast insertion or removal can be physically challenging, unwieldy and risky for one crewmember, since the foot of the mast 10 must be held steady and properly aligned with the receptacle 12 at the critical insertion/removal point otherwise the mast 10 and/or the receptacle 12 can be seriously damaged.
Since weight/strength characteristics of boats generally increase exponentially with boat length by the third power, the associated mast deployment difficulties would nearly double for a 25 foot boat, and more than triple for a 30 foot boat compared to a 20 foot boat; therefore in such larger boats, installing and removing un-stayed type masts manually becomes virtually impossible for one crew member and extremely difficult and skill-dependent even for two.
The capability of manually stepping and un-stepping of un-stayed masts is highly advantageous in avoiding the cost and inconvenience of hiring shore-based equipment such as a crane or travel-lift; however, with the conventional arrangement as shown in FIG. 1, manual stepping and un-stepping continue to prove troublesome, difficult or impractical, depending on the size of the sailboat and mast.